Kaposi’s sarcoma (KS) was originally described in the late 1800’s as a rare and relatively benign neoplasm of elderly men of Jewish or Mediterranean descent. Today, KS is recognized as the most common malignancy in AIDS patients, affecting approximately 20% of human immunodeficiency virus-1 (HIV-1)-positive patients (1-3). AIDS-related KS (also known as epidemic KS) is clinically more aggressive than other forms of KS, including classical (Mediterranean), African (endemic), and iatrogenic immunosuppressive-drug associated with organ transplantation [reviewed in (4,5)]. While often presenting in the skin of HIV-1 positive patients, AIDS-KS lesions can involve internal organs, particularly the lungs and gastrointestinal tract, resulting in severe and potentially fatal hemorrhagic disease (6).
Since the publication of a DNA sequence associated with Kaposi sarcoma, several reports have either supported (18-20,23-25) or refuted (26,27) the notion that this novel DNA virus was important in KS. To date, it had not been possible to propagate this putative virus or even to maintain it in cell culture in the absence of other known herpesviruses, making it difficult to characterize its transmissibility and its host cell range, and to develop anti-viral and diagnostic reagents.
Accordingly, one object of this invention is to provide a method for cultivating KS tumor cells that contain HHV-8 virus in a nonreplicative state.
A second object of the present invention is to provide an intact human herpesvirus derived from AIDS-associated Kaposi’s Sarcoma cells (HHV-8).
A third object of the present invention is to provide methods for propagating human herpesvirus derived from AIDS-associated Kaposi’s Sarcoma cells in vitro.
A fourth object of the present invention is to provide diagnostic methods for detecting human herpesvirus derived from AIDS-associated Kaposi’s sarcoma cells in a patient.
A fifth object of the present invention is to provide methods for screening for antiviral drugs using cells infected with human herpesvirus derived from AIDS-associated Kaposi’s sarcoma cells.
The present inventors have now achieved these and other objects by isolating human herpesvirus and discovering methods for propagating the same. The present inventors utilized growth conditions that allow multiple passages of primary KS cell lines. KSHV, or HHV-8, DNA sequences were detected in early passages of these tumor cells which were nearly identical to the previously described herpes-like DNA sequences (17,19). By co-culture with the human embryonal kidney epithelial cell line, 293 cells, cell-free viral lysate was isolated which induced a cytopathic effect on 293 cells. Characterization of the virus was performed, and propagation by serial passage was confirmed.